This invention relates to a process for repairing slag ladles, as used in the production of iron and steel, which are damaged as a result of thermal and chemical stresses.
Some types of slag ladles are made from hematite or steel iron and, when used, can suffer thermally or chemically produced damage as, apart from the slag to be removed, liquid metal occasionally inadvertently entering with the slag can cause damage too. Because its specific gravity is greater, the liquid metal accumulates at the bottom of the ladle and can cause the ladle material to melt so that considerable erosion takes place over a long period of use, which usually can even be seen on the exterior of the ladle in the form of cracks or holes. The ladle can no longer be used in production and frequently has to be scrapped as no suitable repair processes are available.
Slag ladles damaged in this way cannot be repaired using known welding repair methods.
In one known process for filling the eroded or burnt parts of cast iron or hematite iron ingot and casting moulds, the damaged part is first covered with a layer of cast iron rods and steel electrodes. Then, intermediate spaces are filled by means of a steel electrode with simultaneous melting of a cast iron rod, following which other layers are applied exclusively with a current-carrying cast iron rod. In so far as with this state of the art, and with the present application, these are considered as welding processes, then these belong to the class of so-called cold welding processes. With the aforesaid known method, networks of fine cracks form in the walls of the mould which also continue through the welding material so that finally, cracks are also present in the region of the completely welded over damaged area, so that expansion and contraction is possible without destroying the material. Cracks of this type also occur in the case of slag ladles. However, as the damaged parts are considerably deeper and completely penetrate the wall, use of the known process would means that the complete welded layer would fall out of the bottom of the ladle when contraction took place.